Leading teacher of anatomy dissected amphibian (4)
I believe the answer is:
toad
'amphibian' is the definition.
(I know that toad is a type of amphibian)
'leading teacher of anatomy dissected' is the wordplay.
'leading' indicates taking the first letters.
The first letters of 'teacher of anatomy dissected' is 'TOAD'.
(Other definitions for toad that I've seen before include "Amphibian with warts" , "Contemptible person" , "not found in Ireland" , "Warty amphibian" , "A loathsome person" .)